This invention relates to an apparatus for liquid sampling. In particular, it relates to an apparatus for obtaining a liquid sample from a body of liquid along a depth range, which is representative of the liquid along the entire depth range.
When a liquid, for example oil, is stored in large volumes, the properties and composition of the liquid can vary significantly at different depths. A sample removed from a single point within such a body of liquid will only provide information on the composition at that specific depth within the liquid, and does not provide an accurate representation of the entire body of liquid. Therefore, to obtain accurate readings relating to, and representative of an entire body of liquid, it is necessary to obtain a sample taken along the entire depth of the liquid. Furthermore, it is not sufficient to merely take multiple samples from a number of specified depth points as important variations in the liquid properties along the depth may be ignored. This is particularly important in liquid such as oils in which stratified layers may form.
Accordingly, a number of current sampling systems continuously sample liquid whilst traversing the depth of a body of liquid. Such systems generally comprise a sampling container having multiple sampling apertures located at the top of chamber. As the sampling chamber is lowered through the liquid, the liquid pressure forces liquid into the chamber via one or some of the apertures, while the remaining apertures allow air from within the chamber to escape. However, as the sampling chamber descends within the liquid, the liquid pressure increases, resulting in an increase in flow rate of the liquid into the chamber. Hence, the sampling flow rate is not constant as the container descends along the sampled depth range. As a result, the liquid sample will generally contain a greater volume of liquid from the lower end of the sampling range than from the upper end. Therefore, whilst such systems improve on single depth sampling techniques, they fail to provide samples which are representative of the entire depth range sampled. In addition, as such samplers are raised back through the body of liquid once the sampling has been completed, at least the upper levels of the sample are contaminated as liquid continues to enter the chamber and mix with the sample already taken.
It is therefore desirable to provide an improved system for sampling liquids which addresses the above problems, and provides a sample representative of the entire sample depth range, and/or which provides improvement generally.